Altmanella lenati, Fend, 2009

Fend, En. V., 2009, An evaluation of the genus Kincaidiana Altman, 1936, with the designation of Altmanella n. gen. (Annelida, Clitellata, Lumbriculidae), Zootaxa 2077, pp. 1-30 : 20-26

Altmanella lenati n. sp.

Figures 13–15

Holotype. USNM 1122780 . A whole mounted worm, stained in borax carmine.

Type locality. North Carolina, Carteret Co.: Pettiford Creek at Millis Road, 8-Jan-08, collected by D. Lenat.

Paratypes. USNM 1122781-1122784 . From the type locality, 8-Jan-08, collected by D. Lenat. 1 whole mount, 1 sagittally sectioned, 1 transversely sectioned. North Carolina, Richmond Co.: Drowning Creek at SR 1004, 28-Mar-08, 1 whole mount .

Other material. North Carolina: The type locality, 17-Feb-08, 1 whole mount. 8-Jan-08, 5 whole mounts, 1 dissected, 1 sagittally sectioned. Halifax Co.: Beech Swamp, 17-Mar-07, 1 whole mount. Montgomery Co. : Cedar Creek on River Road , 18-Mar-07, 2 whole mounts. Little River at Star, 18-Mar-07, 2 whole mounts, 2 sagittally sectioned. Unnamed tributary to Little River at Star, 18-Mar-07, 1 whole mount. Richmond Co. : Drowning Creek at SR 1004, 15-Mar-07, 1 whole mount. 28-Mar-08, 1 whole mount. Seep at Drowning Creek , SR 1004. 17-Apr-08, 4 whole mounts. All specimens collected by D. Lenat.

Etymology. Named for David R. Lenat, who has discovered several new species of Lumbriculidae , in addition to other freshwater invertebrates in southeastern North America.

Description. Histological details are based on sectioned worms from Pettiford Creek and Little River. Measurements in the text are means and ranges for all sites.

Small, thin, tapered worms ( Fig. 13A); length (preserved) 14 (11–16) mm; diameter 0.28 (0.20–0.35) mm in IX (at male pore); maximum diameter to 0.32 (0.24–0.40) mm (usually in X–XII), anterior and posterior segments thinner, less than 0.2 mm. Prostomium rounded or rounded-conical ( Fig. 13C). Chaetae paired, in four bundles per segment, beginning in II. All chaetae simple-pointed, moderately sigmoid, with nodulus 0.33–0.41 of the total length from the tip ( Fig. 13B). Chaetal length 88 (70–103) µm anteriorly and in clitellar region, 85 (55–99) µm posteriorly; somewhat shorter in II–III. Secondary segmentation variable, usually a few anterior segments posterior to II have a narrow anterior ring up to 1/4 length of segment ( Fig. 13C), occasionally to IX or more ( Fig. 13A). Segmentation obscured by clitellum in external view, often weak in posterior segments.

Epidermis in anterior segments 7–12 µm thick; many epidermal cells appear enlarged and granular, particularly in middle of some anterior segments. Clitellum distinctly glandular in mature specimens, from mid-IX to mid-XI; absent between and around male pores. Clitellar epidermis thickest (23–33 µm) ventrally in X, anterior to the spermathecal pores ( Figs. 13D, 14B); more dorsally, clitellum 12–24 µm thick. Circular muscle of body wall 1–2 µm thick; longitudinal muscles 8–12 µm thick. Septa indistinct at 1/2–2/3. Pharynx with ventral wall thin; a thickened dorsal pad in II–III ( Figs. 13D, 15A); everted in many preserved specimens. Pharyngeal glands usually in V–VII ( Fig. 13D).

Dorsal blood vessel divides beneath the brain, and the two ventral trunks rejoin near septum 2/3 to form the ventral blood vessel. Highly sinuate, lateral commissural vessels usually visible in II–VIII; they join the dorsal vessel anterior to the chaetae, and join the ventral vessel either near the posterior margin of the originating segment or in the anterior to middle part of the following segment. Lateral vessels difficult to see posterior to VIII, but visible as far back as XI in some specimens; those in IX–X may loop back through several segments within the sperm and egg sacs. Lateral vessels were not visible in posterior segments. Perivisceral blood vessels may form a conspicuous plexus in VII–VIII. Chloragogen begins around VIII.

First nephridia paired on 6/7, second pair on 11/12, then sporadic (approximately every fifth segment) and usually unpaired posteriorly. Nephridia with granular postseptal expansions 40–80 µm long, diameter about 20 µm, followed by a convoluted duct, which may penetrate several posterior segments ventral to the gut ( Fig. 13E). Nephropores with or without a weak terminal vesicle, just anterior to ventral chaetae.

All genital pores paired, on ventral chaetal lines. Male pores in IX, each on a short porophore within a shallow concavity, about midway between ventral chaetae and 9/10 ( Fig. 13D). Spermathecal pores paired in X, inconspicuous, just behind ventral chaetae. Female pores intersegmental on 10/11. Testes paired on anterior septa in IX, ovate, extending to mid-IX; ovaries paired in X, narrow and elongate, often extending into XI within egg sacs. Sperm sacs confluent with egg sacs, extending back to XI– XVII; anterior sperm sacs almost always absent, but in one specimen protruding into VIII. Egg sacs extend to XIV–XX .

Spermathecal ampulla irregularly ovate, length 290 (210–420 µm), width 140 (80–180 µm) ( Fig. 14); in X or XI. A very thin muscle layer surrounds the epithelium; epithelial cells small (5–7 µm) near ectal end of ampulla, but larger and vacuolated entally, to 19–31 µm in some mated specimens ( Fig. 15C). Sperm heads may be directed towards ectal duct within ampulla, remainder of ampulla sparsely filled with unordered sperm or tails; no obvious sperm was present in vacuolated cells of epithelium. Spermathecal duct distinct, tubular, length 260 (205–310) µm; diameter at middle 21 (17–25) µm. Duct formed of tightly packed, regular epithelium, surrounded by a very thin muscle layer ( Fig. 15B). Ectally, the duct may widen slightly, but does not form a distinct vestibule. Female funnels simple, cup-shaped, posterior lip about 70–120 µm high, with thick anterior lip.

Male funnels directed posteriad, extending back into X within the sacs ( Fig. 14). Funnels simple, conical to spoon-shaped, about 60–90 µm long by 30–50 µm wide, histologically distinguished from vasa deferentia by cuboidal cells with dense nuclei. Vasa deferentia relatively short and thick; length of free portion 250 (210–275) µm; width in free portion 24–34 µm; ciliated. Vasa may loop posteriorly, but do not penetrate 9/10 or enter X ( Fig. 14); instead, they enter IX directly from the sperm sacs, becoming appressed to the atrium near the ectal end of the atrium (about 30 µm from the male porophore) ( Fig. 15H–I); vas somewhat flattened, but remains histologically distinct from atrium ( Fig. 15D); width of appressed portion about 20 by 30 µm. The lumen of the vas joins the atrial lumen apically ( Fig. 14B–C). Vasa deferentia with thick (10–12 µm) epithelium having a fibrous appearance and indistinct cell boundaries; nuclei sparse and uneven near the atrium, but denser as the vas approaches the sperm funnel; lumen narrow (5–7 µm) and ciliated.

Atria usually entirely in IX, but may pass through septum 9/10 into X. Total atrium length 290 (200–390) µm. Atria tubular to slightly club-shaped, not divided into distinct duct and ampulla (width in ectal part 17–29 µm; width in ental part 24–34 µm); main (ental) part mostly distinguished by presence of prostate glands. Atrial epithelium of cuboidal to slightly columnar cells; in the main (ental) part these cells appear vacuolated with basal nuclei in mature specimens; lumen narrow, to 5–8 µm wide, and ciliated ( Fig. 15D, F). Muscle layer of atrium thin, (1–2 µm). Prostate glands in irregular, petiolate bundles of up to 20–30 granular cells, loosely covering the ental 2/3 to 3/4 of the atrium; prostate bundles about 40–60 µm long.

Atrial duct protrudes within a short, rounded porophore, 31 (22–43) µm high by 36 (28–46) µm wide ( Fig. 15G–I). Porophores may be conical, dome-shaped, or slightly turbinate, and are present (protruded) in all mature, preserved specimens.

Remarks. Altmanella lenati superficially resembles the western Altmanella species ; its small size, and thin, tapered form is distinctive within southeastern Nearctic worm samples. The male porophores are usually visible on unmounted, mature specimens. The position of the male pores on IX is anterior to that of most other lumbriculids (usually in X), but posterior to that of its congeners (VIII). Internally, the tubular atria with thick vasa deferentia (approximately the atrial diameter) separate this species from all other Nearctic lumbriculids.